This invention relates to an inductance component which is a magnetic device such as a transformer and an inductor and, in particular, to an inductance component comprising a permanent magnet disposed in a magnetic gap formed in a magnetic core.
In order to reduce the size and the weight of an inductance component, it is effective to reduce the volume of a magnetic core comprising a magnetic material. Generally, the magnetic core reduced in size easily reaches magnetic saturation so that a current level handled by a power supply is inevitably decreased. In order to solve the above-mentioned problem, there is known a technique in which the magnetic core is provided with a magnetic gap formed at a part thereof. With this structure, a magnetic resistance of the magnetic core is increased so that the decrease in current level is prevented. In this case, however, the magnetic core is decreased in magnetic inductance.
In order to prevent the decrease in magnetic inductance, proposal is made of a technique related to such a structure that the magnetic core comprises a permanent magnet for generating a magnetic bias. In this technique, a d.c. magnetic bias is given to the magnetic core by the use of the permanent magnet. As a consequence, the number of magnetic lines of flux which can pass through the magnetic gap is increased.
However, the existing inductance component using the permanent magnet is disadvantageous in the following respect. That is, the insertion amount or volume of the permanent magnet disposed in the magnetic gap is determined by a sectional area of a middle leg portion of the magnetic core and the dimension of the magnetic gap. Thus, the magnetic bias given to the magnetic core is inevitably restricted.
It is therefore an object of this invention to provide an inductance component capable of increasing the insertion amount of a permanent magnet to thereby obtain an appropriate magnetic biasing effect without varying the dimension of a magnetic gap.
According to this invention, there is provided an inductance component comprising a magnetic core forming a magnetic circuit having a magnetic gap, an exciting coil wound around the magnetic core, and a permanent magnet disposed in the magnetic gap and greater in sectional area than the magnetic core.